The present invention relates to a fastener unit configured to fasten workpieces, such as boards, to support structures, such as joists, and more particularly to a fastener unit that engages a groove in the side of a board to secure the board to a support structure.
There are a variety of structures, such as decks, platforms and flooring, that include horizontal floors supported by an underlying support structure. The structures typically include boards that are placed side-by-side one another. The boards typically are arranged to extend cross support structures, such as joists, disposed under the boards at an angle, sometimes at a right angle. The boards usually are fastened to the joists using fasteners, such as nails or screws. The nails or screws can frequently become discolored over time, or can work themselves loose from the board and project upward from the board surface. Not only are these results aesthetically displeasing, they can present safety hazards.
Some manufacturers have developed hidden fastener systems that fit loosely within grooves of adjacent boards. These hidden fasteners typically include a biscuit-shaped upper plate having two horizontal flanges that fit into the grooves defined by the sides of adjacent deck boards, a single center hole through which a fastener extends to secure to the underlying joist, and a base that extends downward from the upper plate to an underlying joist. While the horizontal flanges can engage the grooves, these elements typically do not engage those grooves forcibly enough to tack the boards to the underlying joist and prevent them from moving during expansion and contraction under changing temperatures. These systems typically also require a user to manually hold the plate in alignment with one or more grooves of the boards as the fastener is advanced, which can be cumbersome. Depending on the height of the base and the distance of the groove from the board lower surface, sometimes these items can be mismatched so that the flanges do not fit well in or align with the grooves. In addition, the flanges are of a fixed thickness so that if that thickness is mismatched relative to a groove, the plate cannot fit in the groove, let alone secure the board to the underlying joist. Further, where a support structure includes a double or triple joist, with two or more joists positioned immediately adjacent one another, the foregoing fastener systems might not be properly sized to conceal those joists or fit within the associated confined spaces.
Accordingly, there remains room for improvement in the field of fastener units that are configured to secure grooved boards to underlying support structures.